Multiple choice review of basic DNA and genetics topics.

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Student questions and responses follow. The attachment should be IGNORED, as it was provided for verification of original student answers. Instead, I have provided the correct answers and explanations for those answers below each question on the present document.

Correct answers to the questions have been marked by "--correct answer."

1) DNA and RNA are polymers composed of ______ monomers.
a) nucleotide--correct answer
b) fatty acid
c) carbohydrate
d) nucleic acid
e) amino acid

Nucleotides are the structural units of RNA and DNA

2) The backbone of DNA consists of ______.
a) paired nucleotides
b) a repeating sugar-phosphate-sugar-phosphate pattern--correct answer
c) a repeating sugar-nucleotide-sugar-nucleotide pattern
d) a repeating ACTGACTG pattern
e) nitrogenous bases

Chemically, DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds.

3) The DNA double helix is ______.
a) composed of adenine and thymine
b) made up of two polynucleotide strands--answer
c) a puzzle to geneticists
d) composed of two chromosomes
e) composed of adenine and guanine

Polynucleotide strands consist of single nucleotides linked together.

4) RNA contains ______, whereas DNA contains ______.
a) uracil . . . thymine--correct answer
b) adenine . . . guanine
c) nucleotides . . . nucleic acids
d) a deoxyribose sugar . . . a ribose sugar
e) cytosine . . . guanine

The main bases are cytosine, guanine, adenine (DNA and RNA), thymine (DNA) and uracil (RNA).

5) If adenine makes up 20% of the bases in a DNA double helix, what percent of the bases are guanines?
a) 20% b) 30%--correct answer c) 80% d) 40% e) 60%

A pairs with T (20%+20% = 40%) and C pairs with G (100%-40% = 60%/2 = 30%).

6) In a DNA double helix, adenine pairs with ______ and guanine pairs with ______.
a) uracil . . . cytosine
b) thymine . . . cytosine--correct answer
c) cytosine . . . uracil
d) guanine . . . adenine
e) cytosine . . . thymine

See explanation for #5.

7) If one strand of a DNA double helix has the sequence GTCCAT, what is the sequence of the other strand?
a) ACTTGC b) CUGGTU c) CAGGUA d) TGAACG e) CAGGTA--correct answer

See above. (If it was RNA, it would be CAGGUA). Nucleotides in the parent DNA strand pair with their opposite partners in the copied DNA strand.

8) Evidence for the spiral nature of DNA came from ______.
a) X-ray crystallography studies--correct answer
b) studies of pathogenic bacteria
c) transforming studies
d) Bacteriophage studies
e) base rule studies

In 1953, based on X-ray diffraction images taken by Rosalind Franklin and the information that the bases were paired, James D. Watson and Francis Crick suggested what is now accepted as the ...